Objectives: To purify various complement components from normal human sera and to raise specific antisera to them in rabbits. 2. To obtain colostral fluids from mothers of ABO-erythroblastotic infants; to test the secretions for anti-A and anti-B activities by hemagglutination and opsonization of incompatible erythrocytes; and to isolate secretory IgA from active colostra. 3. to study the mechanisms of complement-dependent opsonization by secretory IgA of incompatible human red cells in an effort to determine whether the classical or alternte pathway of complement activation is involved. 4. To identify and quantitate erythrocyte-coating substances (IgG, complement components) in patients with immune hemolytic anemias; to study, by electron microscopy, the membrane ultrastructure of these erythrocytes. 5. To study the membrane characteristics of normal human lymphocytes and peripheral blood lymphocytes obtained from patients with lymphoproliferative disorders and/or autoimmune diseases. In particular, human lymphocytes having membrane characteristics of both B and T cells will be further examined fo their immunobiologic characteristics.